Polyoxymethylene resin is used in wide applications including various structural parts and office automation equipment, as an engineering resin having well-balanced mechanical properties and excellent friction wear performance. Recently, attempts have been made to use such polyoxymethylene resin as material for a ramp in a hard disk drive. For example, Patent Documents 1 and 2 disclose that synthetic resins such as polyoxymethylene are suitable as ramp materials. Patent Document 3 also describes as ramp materials a copolyester (HAHN) between 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, polyoxymethylene, and polyetheretherketone. Patent Document 4 describes, as ramp unit materials, polyimide, polyoxymethylene, PEEK, HAHN, liquid crystal polymers and PTFE-filled plastics. Patent Document 5 discloses an application of a material having a tensile elongation of 30% or more as a ramp material, specifically, a polyoxymethylene resin. Patent Document 6 submitted by the applicants of the present application discloses a ramp for a hard disk formed of a polyoxymethylene resin and a polymer lubricant material.
On other hand, for sealing materials and gasket materials to be used in hard disk devices, as described in Patent Documents 7 and 8, there have been demanded materials low in generation of outgases (corroding gases such as sulfur, bromine and chlorine; and organic gases such as siloxane and olefin) in order to avoid staining of a magnetic or optical disk set in a device. The proportion of the amount of a ramp material to that of a sealing material is from a few tenths to a few hundredths in terms of weight ratio; however, from the viewpoints of the size reduction and high integration of HDD, demand for materials low in outgas and corroding gas generation is conceivably essential.
However, in the aforementioned conventional technologies, no description on the outgases and corroding gases (harmful gases) is found and further, no proposal that considers and attempts to reduce the adverse effect due to the colorant in a polyoxymethylene resin ramp is found.                Patent Document 1: JP-A-10-064205 (U.S. Pat. No. 6,151,190A)        Patent Document 2: JP-A-10-125014 (without family)        Patent Document 3: JP-A-11-339411 (U.S. Pat. No. 6,160,686A)        Patent Document 4: JP-A-2001-23325 (U.S. Pat. No. 6,424,501B1)        Patent Document 5: JP-A-2001-297548 (US2001/0040769A1)        Patent Document 6: WO03-055945        Patent Document 7: JP-A-09-316255 (without family)        Patent Document 8: JP-A-2002-265681 (without family)        Patent Document 9: JP-A-2000-71241 (without family)        